I named it Media Center 24.desktop and used this to autostart normal MC on boot...
[Desktop Entry]
Type=Application
Name=Media Center 24
Comment=JRiver Media Center 24
Exec=/usr/bin/mediacenter24 %F
Terminal=false
StartupWMClass=Media_Center_24
StartupNotify=true
Hidden=false
It works. I tested this too for Media Server...
[Desktop Entry]
Type=Application
Name=Media Center 24
Comment=JRiver Media Center 24
Exec=/usr/bin/mediacenter24 %F /MediaServer
Terminal=false
StartupWMClass=Media_Center_24
StartupNotify=true
Hidden=false
Seems to work too, but it starts MC and minimizes it immediately. Though, honestly, this would be less than ideal since Media Server starts MC in the system tray on Windows and the menu bar on Mac. Of course, it's probably not easy to do on Linux due to differences in desktop environments.
I also tested using sleep like geier22 posted above...
[Desktop Entry]
Type=Application
Name=Media Center 24
Comment=JRiver Media Center 24
Exec=sh -c "sleep 10; /usr/bin/mediacenter24"
Terminal=false
StartupWMClass=Media_Center_24
StartupNotify=true
Hidden=false
This works, so startup delay could be used... now, let's test this with Media Server...
[Desktop Entry]
Type=Application
Name=Media Center 24
Comment=JRiver Media Center 24
Exec=sh -c "sleep 10; /usr/bin/mediacenter24 /MediaServer"
Terminal=false
StartupWMClass=Media_Center_24
StartupNotify=true
Hidden=false
Seems to work too. Now, we can consolidate this to two entries instead of four; Media Center and Media Server. Here's what I'd recommend to use for Media Center (sleep is optional. sleep 0 = no delay)...
[Desktop Entry]
Type=Application
Name=Media Center 24
Comment=JRiver Media Center 24
Exec=sh -c "sleep 0; /usr/bin/mediacenter24"
Terminal=false
StartupWMClass=Media_Center_24
StartupNotify=true
Hidden=false
And here's what I'd recommend to use for Media Server (again sleep is optional. sleep 0 = no delay)...
[Desktop Entry]
Type=Application
Name=Media Center 24
Comment=JRiver Media Center 24
Exec=sh -c "sleep 0; /usr/bin/mediacenter24 /MediaServer"
Terminal=false
StartupWMClass=Media_Center_24
StartupNotify=true
Hidden=false
Tada! I'll test these under Ubuntu, Linux Mint, Arch Linux, etc. It *should* work fine with all of them though.